Oil, grease and solid waste contaminant removal or recovery systems are well known in the prior art. Over the past thirty years there has been a steady move towards reducing the contaminants entering the sewage system, such as at food handling facilities, to reduce the grease and solid waste entering the water flows. Sewer system lines can become clogged from the fats, oil and grease waste materials (hereinafter referred to as “F.O.G.”) put into the sewer system. This has led more and more sewer authorities to implement F.O.G. control programs and regulations in attempts to remove as much F.O.G. as possible from the effluent flow, thereby releasing only grey water to the sewer system.
Historically, grease traps have been used to meet increasing regulation and control program constraints by, particularly in restaurants and other commercial facilities, limiting the amount of grease and solid waste that is carried into sewer systems via waste water. Typical grease traps are either passive grease traps or automatic, active grease removal traps. Active separators remove F.O.G. from the effluent, typically by some type of skimming operation. Passive grease traps may typically store large amounts of the separated grease and are usually only emptied of the stored waste periodically, and, therefore waste tends to build up inside the tank. Passive grease traps typically include a tank with an inlet that brings in waste water and may contain an outlet that carries water out of the system. The grease is separated from the effluent inside the tank. Lightweight grease rises to the top of the tank and heavier solids settle in the bottom of the tank, where they are stored until they can be removed and the tank emptied.
A problem with many grease traps traditionally is that when influx of large amounts of water is flushed through the system with a large velocity, the grease that has already separated is disrupted, causing the grease to be expelled with grey water. This is especially true as the tank fills up with grease, so that the grease/water interface is closer to the grease trap bottom. Therefore, the idea has been to manage the separation of grease from the water to prevent comingling after separation.
Our prior U.S. Pat. No. 7,367,459 discloses an example of a passive grease trap which can be made economically. It has facilities for catching, separating and holding solids and grease so that they can be pumped out at intervals and has proven to be commercially successful.
However, the storage tanks of such grease traps are often extremely large, located underground, difficult to access and/or inadequately emptied when pumped out. It is to these and other issues that this disclosure is directed.